#include <queue>
#include <pthread.h>

template <class T>
class BlockQueue
{
    static const int defalutnum = 20;
public:

    BlockQueue(int maxcap=defalutnum)
        :maxcap_(maxcap)
    {
    pthread_mutex_init(&mutex_,nullptr);
    pthread_cond_init(&c_cond_,nullptr);
    pthread_cond_init(&p_cond_,nullptr);
    //low_water_=maxcap_/3;
    //high_water_=(maxcap_*2)/3;
    }
    T pop()
    {
        pthread_mutex_lock(&mutex_);
        while (q_.size()==0)
        {
            pthread_cond_wait(&c_cond_,&mutex_);
        }

        T out = q_.front();
        q_.pop();
        
        pthread_cond_signal(&p_cond_);
        pthread_mutex_unlock(&mutex_);

        return out;
    }

    void push(const T& in)
    {
        pthread_mutex_lock(&mutex_);
        while (q_.size()==maxcap_)
        {
            pthread_cond_wait(&p_cond_,&mutex_);
        }

        q_.push(in);
        pthread_cond_signal(&c_cond_);
        pthread_mutex_unlock(&mutex_);
        
    }

    ~BlockQueue()
    {
        pthread_mutex_destroy(&mutex_);
        pthread_cond_destroy(&c_cond_);
        pthread_cond_destroy(&p_cond_);
    }

private:
    std::queue<T> q_;
    int maxcap_;
    pthread_mutex_t mutex_;
    pthread_cond_t c_cond_;
    pthread_cond_t p_cond_;

    //int low_water_
    //int high_water_;
};